<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        @keyframes yuan{
            form {
                transform: rotate(0deg);
            }
            to {
                transform: rotate(360deg);
            }
        }
        .big{
            width: 300px;
            height: 300px;
            border-radius: 50%;
            border: 1px solid #000;
            display: flex;
            justify-content: center;
            align-items: center;
            margin: 0 auto;
            background-color: skyblue;
            background: linear-gradient(90deg,skyblue 0%, skyblue 50%, orange 50%, orange 100%);
            
           
        }
        .big:hover{
            animation-name: yuan;
            animation-duration: 3s;
            animation-iteration-count: infinite;
            animation-timing-function:ease;
            animation-direction:alternate;
        }
        .box{
            width: 270px;
            height: 270px;
            background-color: green;
            border-radius: 50%;
            
        }
    </style>
</head>
<body>
   <div class="big">
        <div class="box">

        </div>
   </div>
</body>
</html>